It is desirable for many feeding operations to separate the fibrous portions of a chopped alfalfa plant, i.e., the stem material, from the remaining powdered portion of the plant, i.e., the leaves, because the latter is, relatively speaking, very high in protein while the former is essentially a bulk material with lesser protein and other nutrient value. Although attempts have been made to separate these parts by shaking the fine materials through a screen, it has been the experience of the inventor that no one has accomplished the separation in a manner which is practical and economically feasible.
Two examples of prior art devices used in cutting alfalfa and similar feed materials are disclosed in U.S. Pat. Nos. 943,308 (Jorgensen) and 1,306,500 (Rankin). The Jorgensen patent discloses an alfalfa cutter wherein outer blades rotate and everything is passed through a screen. The Rankin patent discloses a feed material grinder including a series of vertical blades and a screen located therebelow. The devices shown in these two patents are fairly typical of the state of the art.
Separators for other materials are also known. Examples of such separators include those disclosed in U.S. Pat. Nos. 2,267,326 (Eissmann); 2,552,565 (Les Veaux); 2,592,994 (Ahlmann); 3,542,037 (Pietralunga); 3,661,159 (Pietrucci) and 3,899,139 (Okada). Briefly considering these patents, the Eissmann patent discloses an air separator for comminuted tobacco wherein suction is used to draw off the leaf portion from a falling leaf-stem mass. The Les Veaux patent discloses an air swept rotary beater and separator wherein dust is captured in a vortex in the middle of the device and drawn away, with coarse materials being drawn to the outside. The Ahlmann patent similarly discloses a centrifugal grinder providing circulation of the mass and suction removal of the ground material. The Pietralunga patent discloses a cut tobacco stemmer device of the ballistic and pneumatic type, the device providing separation of the light leaf and heavy stem. The Pietrucci patent discloses an apparatus for stemming tobacco leaves and separating the products obtained including a rotary chamber which provides for grinding of the mass sufficiently to permit the light material to be drawn off pneumatically. The Okada patent discloses a crushing apparatus for tires wherein the non-crushable portions are floated by air currents for separation purposes.